JP2015063994A - Internally cooled transition duct aft frame - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an improved internally cooled aft frame for a combustor of a turbomachine, such as a gas turbine.SOLUTION: An aft frame for a transition duct of a gas turbine combustor includes a main body having an outer rail, an inner rail, a first side rail circumferentially separated from an opposing second side rail, a forward portion, an aft portion and an outer surface. An inlet port extends through the outer surface, and an exhaust port extends through the forward portion. A serpentine cooling passage is defined within the main body beneath the outer surface. The serpentine cooling passage is in fluid communication with the inlet port and the exhaust port. A conduit may be connected to the exhaust port for routing a compressed working fluid away from the aft frame.

Description

  The present invention relates generally to gas turbine combustors. More particularly, the invention relates to an internally cooled rear frame of a transition duct mounted in a combustor.

  A turbomachine, such as a gas turbine, generally includes an inlet section, a compressor section, a combustion section that includes a plurality of combustors, a turbine section, and an exhaust section. The inlet section cleans and regulates the working fluid (eg, air) and supplies this working fluid to the compressor section. The compressor section gradually increases the pressure of the working fluid and supplies high pressure compressed working fluid to a compressor discharge casing that at least partially surrounds each of the combustors.

  The fuel is mixed with a high pressure compressed working fluid and the mixture is combusted in a combustion chamber defined within each combustor to produce a hot, high pressure combustion gas. The combustion gas flows into the turbine section where the combustion gas expands and works along a hot gas path defined within the compressor discharge casing. For example, combustion gas expansion in the turbine section can cause a shaft connected to the generator to rotate to generate electricity.

  The hot gas path is at least partially defined by an annular inner cylinder and / or a transition duct. The transition duct may be provided as part of the transition piece assembly. A conventional transition piece assembly includes an outer impact sleeve that circumferentially surrounds an annular transition duct. A cooling ring is defined between the outer impingement sleeve and the transition duct. The downstream end of the transition piece assembly terminates at an inlet port to the turbine.

  A rear frame or support member extends circumferentially outward, generally radially and around the downstream end of the transition piece assembly. In general, the rear frame is mounted to the casing, inner support ring and / or turbine to provide mounting support for the transition piece assembly and to reduce transition duct deformation. In operation, the rear frame is directly exposed to hot combustion gases. As a result, various cooling schemes have been developed to enhance the thermal mechanical performance of the rear frame.

  One conventional cooling scheme is that a portion of the high pressure compressed working fluid is discharged from the compressor and routed from the casing through a path through one or more cooling channels defined in the rear frame, and the high pressure compressed working fluid is heated to a high temperature. Including venting into the gas path and / or the cooling ring. In that case, the exhausted compressed working fluid may be used to cool the transition duct and / or the inner cylinder. Further, the compressed working fluid may be routed through a cooling ring to a combustion chamber for mixing with combustion fuel.

  One limitation of conventional cooling schemes is that the shape and / or complexity of the internal cooling channel is limited to a single channel or a generally linear cooling channel in the rear frame. For example, conventional cooling passes through a generally linear inlet port that supplies cooling air to a linear cooling channel and exits the rear frame through an exhaust port. This linear or single run of compressed working fluid through the cooling channels limits the cooling capacity of each cooling channel. Furthermore, current manufacturing processes require costly and time consuming secondary operations such as milling or electrical discharge machining to cut the cooling channels and / or inlet and outlet ports into the rear frame. , Thus increasing the manufacturing cost.

  A second limitation of existing cooling schemes can be prevalent when there are obstacles such as fuel injectors or other vortex generators in the cooling ring, and therefore between the rear frame exhaust port and the combustion chamber. There is a pressure loss of the high pressure compressed working fluid that can be measured. Another potential limitation of existing cooling schemes may be that optimized cooling cannot be provided if the location and orientation of the exhaust port exceeds the rear frame region. Thus, it would be useful to have an improved internal cooling rear frame for a turbomachine combustor such as a gas turbine.

US Pat. No. 8,418,474

  Aspects and advantages of the invention are set forth in the following description, may be apparent from the description, or may be learned from practice of the invention.

  One embodiment of the present invention is a rear frame for a gas turbine combustor transition duct. The rear frame includes a body having an outer rail, an inner rail, a first side rail spaced circumferentially from an opposing second side rail, a front portion, a rear portion, and an outer surface. An inlet port extends through the outer surface and an exhaust port extends through the front portion. A serpentine cooling channel is defined in the body below the outer surface. The serpentine cooling channel is in fluid communication with the inlet port and the exhaust port.

  Another embodiment of the invention is a transition piece assembly. The transition piece assembly includes a transition duct having an upstream end and a downstream end, an outer sleeve extending circumferentially around the transition duct, and a cooling ring defined between the transition duct and the outer sleeve. A rear frame that is integral with the downstream end of the transition duct and a front edge of the outer sleeve. The rear frame includes a main body including an outer rail, an inner rail, a first side rail spaced circumferentially from the opposing second side rail, a front portion, a rear portion, and an outer surface. An inlet port extends through the outer surface and an exhaust port extends through the front portion. The exhaust port is in fluid communication with the cooling ring. A serpentine cooling channel is defined within the body of the rear frame and extends below the outer surface. The serpentine cooling channel is in fluid communication with the inlet port and the exhaust port.

  Another embodiment of the invention is a gas turbine. The gas turbine includes a compressor at an upstream end of the gas turbine and a combustion section disposed downstream from the compressor. The combustion section includes a combustor and an outer casing that at least partially surrounds the combustor and is in fluid communication with the compressor. The gas turbine further includes a turbine disposed downstream from the combustor. The combustor includes a fuel nozzle and a combustion chamber defined downstream from the fuel nozzle. For example, the combustion chamber may be defined by an inner cylinder or the like. A transition duct extends downstream from the combustion chamber. The transition duct includes an upstream end closest to the combustion chamber and a downstream end that terminates at the inlet to the turbine. The outer sleeve extends circumferentially around the transition duct and defines a cooling annulus therebetween. The combustor further includes a rear frame that is integral with the downstream end of the transition duct and a front edge of the outer sleeve. The rear frame includes a front portion, a rear portion, an outer surface, an inlet port extending through the outer surface, an exhaust port extending through the front portion and in fluid communication with the cooling ring, and within the body under the outer surface. And a body defining a serpentine cooling channel defined by: The serpentine cooling channel is in fluid communication with the inlet port and the exhaust port.

  Those skilled in the art will better understand the features and aspects, such as such embodiments, upon review of the specification.

  The complete and privileged disclosure of the present invention to those skilled in the art, including its best mode, is more specifically described in the remainder of the specification, including reference to the accompanying figures.

1 is a functional block diagram of an exemplary gas turbine that is within the scope of the present invention. FIG. 1 is a vertical cross-sectional view of a portion of an exemplary gas turbine, including an exemplary combustor that may include various embodiments of the present invention. 3 is a perspective view of an exemplary transition duct and exemplary rear frame of the combustor shown in FIG. 2 in accordance with various embodiments of the present invention. FIG. FIG. 4 is a vertical cross-sectional view of a portion of the rear frame taken along section line 4-4 shown in FIG. 3 according to one embodiment of the present invention. FIG. 4 is a cross-sectional overhead view illustrating any one of the outer rail, the inner rail, the first side rail portion or the second side rail portion of the rear frame shown in FIG. 3 according to various embodiments of the present invention. FIG. 3 is a vertical cross-sectional view of a portion of the combustor shown in FIG. 2 according to one embodiment of the invention.

  Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerals and letter symbols to refer to features in the drawings. Equivalent or similar symbols in the drawings and description are used to refer to equivalent or similar parts of the invention.

  As used herein, the terms “first”, “second” and “third” may be used interchangeably to distinguish one component from another. It is not intended to imply the location or importance of individual components. The terms “upstream” and “downstream” refer to the relative direction of fluid flow in the fluid path. For example, “upstream” means the direction in which the fluid flows therefrom, and “downstream” means the direction in which the fluid flows. The term “radially” means a relative direction that is perpendicular to the centerline of the axis of a particular component, and the term “axially” is the centerline of the axis of a particular component It means a relative direction that is almost parallel.

  Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For example, features illustrated or described as part of one embodiment may be used in another embodiment to provide another embodiment. Accordingly, the present invention is intended to embrace such alterations and modifications that fall within the scope of the appended claims and their equivalents. While exemplary embodiments of the present invention are generally described in the context of a combustor incorporated into a gas turbine for purposes of illustration, those skilled in the art will recognize embodiments of the present invention particularly within the scope of the claims. It will be appreciated that, unless described, it may be applied to any combustor incorporated in any turbomachine and is not limited to a gas turbine combustor.

  Referring now to the drawings in which the same number represents the same elements throughout the figures, FIG. 1 illustrates a functional block diagram of an exemplary gas turbine 10 that may incorporate various embodiments of the invention. provide. As shown, the gas turbine 10 generally includes a series of filters, cooling coils, moisture separators, and / or others for cleaning and otherwise conditioning the working fluid (eg, air) 14 entering the gas turbine 10. An inlet section 12 that may include the following devices: The working fluid 14 flows to the compressor section where the compressor 16 gradually distributes kinetic energy to the working fluid 14 to produce a compressed working fluid 18.

  The compressed working fluid 18 is mixed with fuel 20 from a fuel source 22 such as a fuel skid to form a combustible mixture within one or more combustors 24 of the combustion section 26 of the gas turbine 10. The combustible mixture is burned to produce high temperature, high pressure and high speed combustion gas 28. Combustion gas 28 flows through turbine 30 in the turbine section to produce work. For example, the turbine 30 may be connected to the shaft 32 such that rotation of the turbine 30 drives the compressor 16 to generate the compressed working fluid 18.

  Alternatively or additionally, the shaft 32 may connect the turbine 30 to the generator 34 to generate electricity. Exhaust gas 36 from turbine 30 flows through an exhaust section 38 that connects turbine 30 to exhaust stack 40 downstream from turbine 30. The exhaust section 38 may include, for example, an exhaust heat recovery device (not shown) for cleaning and extracting additional heat from the exhaust gas 36 prior to release to the environment.

  FIG. 2 provides a vertical cross-sectional view of a portion of a gas turbine 10 that includes an exemplary combustor 24 that may be incorporated into various embodiments of the present invention. As shown in FIG. 2, the combustion section 26 includes an outer casing 50, such as a compressor discharge casing, disposed downstream of the compressor 16. The outer casing 50 at least partially surrounds the combustor 24. Outer casing 50 at least partially defines a high pressure plenum 52 that at least partially surrounds combustor 24. The high pressure plenum 52 is in fluid communication with the compressor 16 to receive the compressed working fluid 18 from the compressor 16 during operation of the gas turbine 10.

  The end cover 54 may be connected to the outer casing 50. Specifically, in the combustor design, end cover 54 is in fluid communication with fuel source 22. A fuel nozzle 56 in fluid communication with the end cover 54 and / or the fuel source 22 extends downstream from the end cover 54. A fuel nozzle 56 extends generally axially through an annular cap assembly 58 disposed within the outer casing 50. An annular liner 60, such as an inner cylinder or transition duct, at least partially defines a combustion chamber 62 in the combustor 24 downstream from the outlet end 64 of the fuel nozzle 56. A flow sleeve 66 may circumferentially surround at least a portion of the liner 60. The flow sleeve 66 is radially spaced from the liner 60 and defines a flow path 68 therebetween. The flow path 68 is in fluid communication with the combustion chamber 62 via the head end portion 70 of the combustor 24. The head end portion 70 may be at least partially defined by the end cover 54 and / or the outer casing 50.

  A transition duct 72 extends downstream from the combustion chamber 62. The transition duct 72 includes an upstream end 74 that is axially spaced from the downstream end 76. In certain configurations, the upstream end 74 surrounds a downstream portion 78 of the annular liner 60. The downstream end 76 of the transition duct 72 terminates closest to the inlet 80 of the turbine 30. Annular liner 60 and / or transition duct 72 define at least partially a hot gas path 82 for delivering combustion gas 28 in a path from combustion chamber 62 through high pressure plenum 52 and into turbine 30.

  In certain embodiments, an outer sleeve 84, such as an impact sleeve or flow sleeve, extends circumferentially around the transition duct 72. The outer sleeve 84 is radially spaced from the transition duct 72 and defines a cooling ring 86 therebetween. The outer sleeve 84 may include a plurality of cooling holes 88 or cooling channels that provide fluid communication between the high pressure plenum 52 and the cooling ring 86. In one embodiment, the cooling ring 86 is in fluid communication with the combustion chamber 62. In certain configurations, the cooling ring 86 is in fluid communication with or fluidly coupled to the combustion chamber 62 via at least one of the flow path 68, the head end portion 70 of the combustor 24, and / or the fuel nozzle 56. doing.

  In certain combustors, one or more fuel injectors 90, also commonly known as rate lean fuel injectors, can inject fuel into the hot gas path 82 downstream from the combustion chamber 62. May extend through outer sleeve 84, cooling ring 86 and transition duct 72. Additionally or alternatively, fuel injector 90 extends through flow sleeve 66, flow path 68 and liner 60 to allow fuel injection downstream from combustion chamber 62 into hot gas path 82. Also good. In addition or in the alternative, other penetrations such as connecting tubes, igniters, pressure probes and flame detectors may act as vortex generators within the flow annulus 86, thus creating a wake or other disturbance in the flow. there's a possibility that.

  In certain embodiments, the rear frame 92 is located at or closest to the downstream end 76 of the transition duct 72. FIG. 3 shows a perspective view of an exemplary transition duct 72 and an exemplary rear frame 92 according to various embodiments of the present invention. As shown in FIGS. 2 and 3, the rear frame 92 is integral with the downstream end 76 of the transition duct 72. As shown in FIG. 2, a portion of the outer sleeve 84, such as the leading edge 94, may be integral with or connected to the rear frame 92 to at least partially define the cooling annulus 86. Good.

  The rear frame 92 and the transition duct 72 may be manufactured as a single component. Alternatively, the rear frame 92 may be connected to the transition duct 72 by welding, brazing, or some other suitable process. In one embodiment, the transition duct 72, the outer sleeve 84, the cooling ring 86 and the rear frame 92 may be provided as a transition piece assembly 96. The rear frame 92 generally provides structural support to reduce and / or prevent deformation of the downstream end 76 of the transition duct 72 during operation of the combustor. Additionally or alternatively, the rear frame 92 may provide a means for mounting the transition duct 72 within the outer casing 50.

  As shown in FIG. 3, the rear frame 92 includes a main body 100. The main body 100 includes an outer rail 102, an inner rail 104, and a first side rail 106 that is circumferentially spaced from an opposing second side rail 108. The body 100 has a front portion 110 separated from the rear portion 112 and an outer surface extending at least partially between the front portion 110 and the rear portion 112 around an outer parameter of the body 100. And a surface 114. The rear frame 92 may also include an attachment mechanism 116 for attaching the transition duct 72 and / or the transition piece assembly 96 (FIG. 2) within the gas turbine 10.

  FIG. 4 provides a vertical cross-sectional view of a portion of the rear frame 92 taken along section line 4-4 shown in FIG. In various embodiments, the body 100 defines an inlet port 118 that extends through the outer surface 114 and an exhaust port 120 that extends through the front portion 110. Inlet port 118 is in fluid communication with high pressure plenum 52 (FIG. 2). The exhaust port 120 is in fluid communication with the cooling ring 86.

  Inlet port 118 and exhaust port 120 are shown on a portion of outer rail 102 for exemplary purposes only. In certain embodiments, the inlet port 118 may be disposed along the outer surface 114 on any one of the outer rail 102, the inner rail 104, the first side rail 106, or the second side rail 108. In certain embodiments, the exhaust port 120 may be disposed along the forward portion 110 on any one of the outer rail 102, the inner rail 104, the first side rail 106, or the second side rail 108.

  FIG. 5 provides a cross-sectional overhead view representing any one of the outer rail 102, the inner rail 104, the first side rail 106, or the second side rail 108 according to various embodiments of the present invention. In certain embodiments, the body 100 at least partially defines a serpentine cooling channel 122 that extends below the outer surface 114. Serpentine cooling channel 122 is in fluid communication with inlet port 118 (FIG. 4) and exhaust port 120 (FIGS. 4 and 5) and high pressure plenum 52 (FIG. 2) and cooling ring 86 (FIGS. 2, 4 and 5). ) To enable fluid communication.

  The serpentine cooling channel 122 may be defined in the body 100 by various manufacturing processes. For example, the serpentine cooling channel 122 may be cast using the body 100 coring technique, machined and / or produced by three-dimensional (3-D) printing and / or additional manufacturing processes.

  In certain embodiments, as shown in FIG. 5, the serpentine cooling channel 122 may bend more than once within the body 100 between the front portion 110 and the rear portion 112 below the outer surface 114. As shown, the inlet port 118 may supply a plurality of serpentine cooling channels 122. Further, the exhaust port 120 may exhaust compressed working fluid from two or more serpentine cooling channels 122.

  In one embodiment, the serpentine cooling channel 122 is at least partially defined within the outer rail 102. In one embodiment, the serpentine cooling channel 122 is at least partially within the inner rail 104. In one embodiment, the serpentine cooling flow path 122 is defined at least partially within the first side rail 106. In another embodiment, the serpentine cooling channel 122 is at least partially defined within the second side rail 108.

  In certain embodiments, as shown in FIGS. 4 and 5, a conduit 124 is coupled to or in fluid communication with the exhaust port 120 of the rear frame 92. In one embodiment, the conduit 124 extends across the outer surface 126 of the transition duct 72 toward the upstream end 74 of the transition duct 72, as shown in FIG. A conduit 124 extends between the outer sleeve 84 and the transition duct 72 in the cooling ring 86 (FIG. 2). In certain embodiments, the plurality of conduits 124 are in fluid communication with the corresponding exhaust port 120, but each conduit 124 may extend across the outer surface 126 of the transition duct 72. A conduit 124 extends toward the flow path 68 in the cooling ring 86 so that the compressed working fluid 18 can be routed through or behind various vortex generators. Also good.

  The fluid conduit 124 may extend generally linearly and / or bend. The fluid conduit 124 may include a cooling hole 128 that allows a portion of the compressed working fluid 18 to flow out of the conduit 124 in a particular arrangement along the outer surface 126 of the transition duct 72. In certain embodiments, the fluid conduit 124 provides fluid between the exhaust port 120 and the cooling ring 86, the flow path 68, the head end portion 70 of the combustor 24, and / or the combustion chamber 62. Enable communication.

  FIG. 6 is a vertical cross-sectional view of a portion of the combustor 24 shown in FIG. 2 according to one embodiment of the present invention. As shown in FIG. 6, the conduit 124 may extend from the rear frame 92 toward the combustion chamber 62 and / or the head end portion 70 of the combustor 24. In certain embodiments, conduit 124 may extend past fuel injector 90 and / or flow path 68 in cooling ring 86.

  In operation, the compressed working fluid 18 flows from the compressor 16 into the high pressure plenum 52 as shown in FIGS. A portion of the compressed working fluid 18 flows through the cooling holes 88 and into the cooling ring 86 to provide impact and / or film cooling to the outer surface 126 of the transition duct 72. The compressed working fluid 18 is then routed through the flow path 68 toward the combustion chamber 62, thus providing further cooling to the liner 60 in the reverse direction before reaching the head end portion 70 of the combustor 24. give.

  The compressed working fluid 18 is routed through and / or around the fuel nozzle 56 and mixed with the fuel 20. The premixed fuel 20 and the compressed working fluid 18 flow into the combustion chamber 62 and are combusted to produce combustion gas 28. Combustion gas 28 flows into turbine 30 through hot gas path 82 defined by liner 60 and / or transition duct 72.

  Another portion of the compressed working fluid 18 flows from the high pressure plenum 52 through the inlet port of the rear frame 92 and into the serpentine cooling channel 122. As the compressed working fluid 18 flows or winds between the front portion 110 and the rear portion 112 of the rear frame 92, thermal energy is transferred to the compressed working fluid 18, thus reducing thermal stress on the rear frame 92. Is done. The serpentine or serpentine path defined by the serpentine cooling channel 122 enhances the cooling capacity of the compressed working fluid 18 flowing therethrough compared to conventional linear and / or stepped cooling channels.

  In a conventional rear frame cooling scheme, the compressed working fluid 18 is evacuated closest to the front portion 110 of the rear frame 92, in which case the compressed working fluid 18 passes through the outer cooling holes 88 or impingement sleeve 84 from the high pressure plenum 52. It is taken up by the compressed working fluid 18 that flows directly into the cooling ring 86. However, various obstructions in the cooling ring 86 and / or the flow path 68 such as the fuel injector 90, connecting tube, igniter, pressure probe and flame detector may cause the compressed working fluid 18 from the high pressure plenum 52 to the combustion chamber. When in communication with 62, it results in a measurable pressure loss of the compressed working fluid 18, thus affecting the overall performance of the combustor 24. In addition, these obstacles also disturb the flow field of the compressed working fluid 18 and thus create hot spots along various portions of the transition duct 72 and / or the inner cylinder 60.

  In certain embodiments, the compressed working fluid 18 flows from the exhaust port 120 into the conduit 124 and carries the compressed working fluid 18 downstream from the rear frame 92 into the cooling ring 86. In one embodiment, conduit 124 extends past fuel injector 90 to reduce pressure loss between exhaust port 120 and combustion chamber 62, thereby improving the overall performance of combustor 24. . In other embodiments, the compressed working fluid 18 flows from the exhaust port 120 through the conduit 124, in which case a portion of the compressed working fluid 18 flows through the cooling holes 128 and the transition duct 72 outer surface 126 and / or liner 60. Gives you local or precise cooling. For example, cooling holes 128 may be located adjacent to various hot spots formed along the transition duct and / or liner 60 due to various obstructions in the cooling annulus 86 and / or flow path. Thus, thermal stress on the transition duct 72 and / or liner 60 is reduced.

  This written description uses examples to disclose the invention, including the best mode, and also to make and use the apparatus or system and to implement the methods incorporated. Allows implementation of the present invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples include structural elements that do not differ from the written language of the claims, or include structural elements that are substantially different and equivalent from the written language of the claims. If so, it is within the scope of the claims.

DESCRIPTION OF SYMBOLS 10 Gas turbine 12 Inlet section 14 Working fluid 16 Compressor 18 Compressed working fluid 20 Fuel 22 Fuel source 24 Combustor 26 Combustion section 28 Combustion gas 30 Turbine 32 Shaft 34 Generator 36 Exhaust gas 38 Exhaust section 40 Exhaust stack 50 Outer casing 52 High pressure Plenum 54 End cover 56 Fuel nozzle 58 Annular cap assembly 60 Annular liner, liner (inner cylinder or transition duct)
62 Combustion chamber 64 Outlet end 66 Flow sleeve 68 Flow path 70 Head end portion 72 Transition duct 74 Upstream end 76 Downstream end 78 Downstream portion 80 Inlet 82 Hot gas path 84 Outer sleeve (impact sleeve or flow sleeve)
86 Cooling ring 88 Cooling hole 90 Fuel injector 92 Rear frame 94 Front edge 96 Transition piece assembly 100 Body 102 Outer rail 104 Inner rail 106 First side rail 108 Second side rail 110 Front portion 112 Rear portion 114 Outer surface or surface 116 Mounting mechanism 118 Inlet port 120 Exhaust port 122 Meander cooling channel 124 Conduit, fluid conduit 126 Outer surface 128 Cooling hole

Claims (20)

A rear frame (92) for the transition piece of the gas turbine (10),
a. Outer rail (102), inner rail (104), first side rail (106) circumferentially separated from opposing second side rail (108), front portion (110), rear portion (112) And a body (100) including an outer surface (114);
b. An inlet port (118) extending through the outer surface (114);
c. An exhaust port (120) extending through the front portion (110);
d. Under the outer surface (114), a serpentine cooling channel (122) defined in the body (100) in fluid communication with the inlet port (118) and the exhaust port (120) A rear frame (92) comprising a cooling channel (122).   The meandering cooling channel (122) bends more than once in the body (100) between the front part (110) and the rear part (112) under the outer surface (114). The rear frame (92) of claim 1.   The rear frame (92) of claim 1, wherein the serpentine cooling channel (122) is at least partially defined within the outer rail (102).   The rear frame (92) of claim 1, wherein the serpentine cooling channel (122) is at least partially defined within the inner rail (104).   The rear frame (92) of claim 1, wherein the serpentine cooling flow path (122) is at least partially defined in the first side rail (106).   The rear frame (92) of claim 1, wherein the serpentine cooling flow path (122) is at least partially defined within the second side rail (108).   The rear frame (92) of claim 1, further comprising a conduit (124) coupled to the exhaust port (120). A transition piece assembly (96) comprising:
a. A transition duct (72) having an upstream end (74) and a downstream end (76);
b. An outer sleeve (84) extending circumferentially around the transition duct (72);
c. A cooling ring (86) defined between the transition duct (72) and the outer sleeve (84);
d. A rear frame (92) integral with the downstream end (76) of the transition duct (72) and the front edge (94) of the outer sleeve (84),
i. Outer rail (102), inner rail (104), first side rail (106) circumferentially separated from opposing second side rail (108), front portion (110), rear portion (112) And a body (100) including an outer surface (114);
ii. An inlet port (118) extending through the outer surface (114);
iii. An exhaust port (120) extending through the forward portion (110) and in fluid communication with the cooling ring (86);
iv. A serpentine cooling flow path (122) defined within the body (100) under the outer surface (114) in fluid communication with the inlet port (118) and the exhaust port (120) Transition piece assembly (96) comprising a rear frame (92) comprising a flow path (122).   The serpentine cooling channel (122) bends more than once in the body (100) between the front portion (110) and the rear portion (112) under the outer surface (114). A transition piece assembly (96) according to claim 8,.   The transition piece assembly (96) of claim 8, wherein the serpentine cooling flow path (122) is at least partially defined within the outer rail (102).   The transition piece assembly (96) of claim 8, wherein the serpentine cooling flow path (122) is at least partially defined within the inner rail (104).   The transition piece assembly (96) of claim 8, wherein the serpentine cooling channel (122) is at least partially defined in the first side rail (106).   The transition piece assembly (96) of claim 8, wherein the serpentine cooling flow path (122) is defined at least partially within the second side rail (108).   The transition piece assembly (96) of claim 8, further comprising a conduit (124) coupled to the exhaust port (120).   The conduit (124) extends in the cooling ring (86) over the outer surface (126) of the transition duct (72) toward the upstream end (74) of the transition duct (72). A transition piece assembly (96) according to claim 1. A gas turbine (10),
a. A compressor (16);
b. A combustion section (26) disposed downstream from the compressor (16), comprising a combustor (24) and an outer casing (50) at least partially surrounding the combustor (24), the outer A combustion section (26) in which a casing (50) is in fluid communication with said compressor (16);
c. A turbine (30) disposed downstream from the combustion section (26),
d. The combustor (24),
i. A fuel nozzle (56) and a combustion chamber (62) defined downstream from the fuel nozzle (56);
ii. A transition duct (72) extending downstream from the combustion chamber (62) having a downstream end (76) terminating at an inlet (80) to the turbine (30);
iii. An outer sleeve (84) extending circumferentially around the transition duct (72) and defining a cooling ring (86) therebetween;
iv. A rear frame (92) integral with the downstream end (76) of the transition duct (72) and the front edge (94) of the outer sleeve (84), a front portion (110), a rear portion (112) ), An outer surface (114), an inlet port (118) extending through the outer surface (114), an exhaust port (120) extending through the front portion (110) and in fluid communication with the cooling ring (86). And a serpentine cooling channel (122) defined in the body (100) under the outer surface (114), in fluid communication with the inlet port (118) and the exhaust port (120) A gas turbine (10) comprising a rear frame (92) having a body (100) defining a serpentine cooling channel (122).   The serpentine cooling channel (122) bends twice or more in the body (100) between the front portion (110) and the rear portion (112) under the outer surface (114). A gas turbine (10) according to claim 16.   The rear frame body (100) includes an outer rail (102), an inner rail (104), and a first side rail (106) circumferentially separated from an opposing second side rail (108). The serpentine cooling channel (122) is at least partially defined, the outer rail (102), the inner rail (104), the first side rail (106) or the second side surface. The gas turbine (10) of claim 16, wherein the gas turbine (10) is one or more of the rails (108).   17. A conduit (124) coupled to the exhaust port (120), the conduit (124) extending within the cooling ring (86) over the outer surface (126) of the transition duct (72). A gas turbine (10) according to claim 1.   The conduit (124) coupled to the exhaust port (120), the conduit (124) allowing fluid communication between the exhaust port (120) and the combustion chamber (62). A gas turbine (10) according to claim 16.